Orcen — New Sauroid Fish. 107 



that it was not until after tlie upheaval and denudation of 

 the deposits {x 4', x 4:", and x 4/"), that the denuded Chalk 

 of the south of England, and of the north of France, was laid 

 dry, and the valleys of the Weald, of the Somme, and of the 

 Seine were cut through it. We should also see that the great 

 convulsions which, exerted in a rectilinear direction, thus broke up 

 and destroyed the original curvilinear valley of the Eastern Thames, 

 were equalled, and even surpassed, by others of contemporaneous 

 date and like rectilinear character, which in other parts also broke 

 up ox modified the curvilinear troughs of denudation into which the 

 surface had been furrowed by the elevation and denudation of the 

 Upper Drift sea-bed. 



Erratusi. — In the first part of this, article, which appeared last 

 month, at page 60, line 23 from top, for " west/' read " east" — 

 S. V. W., Jtjn. 



III. — On a Genus and Species of Sauroid Fish {Bitaxiodvs 



IMPAK,^ Ow.) FROM THE KiMMERIDGE ClAY OF CuLHAM, 



Oxfordshire. 



By Professor Owen, F.E.S., F.G.S, etc. 



(PLATES IV. AND Y.) 



THE generic name of the Sauroid Pish, here indicated by portions 

 of jaws, relates to the unusually well-marked arrangement of 

 the teeth on the dentary bone in two' almost parallel ranks along 

 the whole of its alveolar border. The outer rank (Plate V. fig. 1) 

 consisting of few and large teeth ; the inner rank of small ones in 

 greater number. 



It is by no means uncommon in, and is almost peculiar to, the 

 class of Fishes, to have two or more teeth on the same transverse 

 parallel of the dentigerous surface of the same jaw-bone ; but I 

 have not, hitherto, observed two such ranks, so extensive, well- 

 defined, and differentiated in regard to size and curve, as in the 

 present Sauroid genus. 



This additional and very interesting example of a destructive 

 order of Ganoid, from the Kimmeridge Clay, was obtained from 



to X i" ; whereas, althougli the four first-named valleys contain occasional patches of 

 gravel analogous in position to that described as x 2, nothing in any way corresponding 

 to the Thames gravel (x 4") exists in them, while, in the case of the gravel-less 

 valleys of the Crouch and Blackwater, it can be distinctly shown that both of these 

 valleys, for two or three miles of their course (but in the case of the Blackwater on 

 its south side only), cut like the Thames mouth at riffht angles through the " East 

 Essex gravel." The terracing down of this East Essex gravel into the valley of the 

 Weald ; first to beds analagous to a; 5 and x 5', then to the gravels of the Lower 

 Green Sand terrace, around Maidstone, and, lastly, to the gravels of the Weald Clay 

 bottom, prior to the reversal ensuing on the formation of Sea Reach, may be distinctly 

 shewn; as the terracing of the Thames gravel, may, in like manner, be traced 

 through the Darent and Cray VaUey beds, to the gravels of the Lower Green Sand 

 terrace near Sevenoaks. 

 1 Sis, double ; rd^is, rank ; 'oSovs, tooth. 



